Back seat heater takes forever to get warm

[onecrazyfoo4u]

Just got back from a trip to Idaho where it was 0deg or below every night. I live in sunny california, so the heater doesn't get used that much over here. In Idaho I noticed it would take a good 15 minutes of driving around before the rear would produce good heat (with full heat selected and upper vents only). I tried it set to Auto climate control and it was the same. Yet up front, I was getting good heat after just a couple minutes of driving around.

Is this the norm? Why would it take so long to get good heat to the second and third rows?

[Mcgusto82]

It's normal. The DJ uses the heater core upfront yo warm up the rear vents.

Longer distance, different routing..

Not really sure, but it is normal.

Correction.. It's normal IN THIS CAR.

The grand caravan has an auxiliary heater in the rear, snd it warms up like a champ.

Edited January 1, 2014 by Mcgusto82

[onecrazyfoo4u]

So the rear heater is hooked up to the same heater core as the front heater? It routes coolant ~10ft to the back of the car? I thought it was a totally indepent unit in the back...

[webslave]

AFAIK, the Journey's optional rear heat and cooling is just like the units used in the Caravans and Town and Country units. Consisting of its own heater and air conditional cores and evaporators, fans and housings. These units also are fairly small as they have to fit in the side space between the inner panel and the oustide bodywork without intrusion into the enterior space. Also unfortunately, the heater core (and A/C coolant) are, indeed, piped from the engine compartment and use the engine's heat to warm the water in pipes. This leads to two issues, really, the one is that the heat is diverted to the front seats first (it does no good to heat the rear while the front (read driver) is below freezing and the second being the long run that the warm water must make to get to the rear of the car. Lots of temperature loss to the warming the lines, bleed to the air around them, etc. before it ever gets to the rear of the car. From what I understand and what I've found with my unit; the colder it is, the longer it takes to get warm, let alone "hot" water to that rear core takes ~15 minutes, particularly when it is really cold outside. That is going to be true for any design that relies on hot water from the engine; the only way to get around the delay would be to use electric heat for the rear, but, that brings on its own issues (larger alternator, heavier battery, electric wiring capable of higher amperage and possible shorts and the resultant fire...). In order to use hot water as the supply medium for the rear heater, it has to come from the engine (where else are you going to economically get it?) and it takes time to get that additional volume warm and then get it piped to the back while losing heat to the pipes and surrounding air.

[onecrazyfoo4u]

Well I guess it all makes sense. I just haven't experienced it yet since the DJ hasn't seen below 0deg weather before. Glad that mine is working like it should be (even if it sucks).

You would think just using a much larger heater core/fan/blower up front, and splitting between front/rear ducting would be much more efficient. You wouldn't need an entire secondary system or piping coolant to the back of the car. And it would heat up much faster since air would be blowing through ducting inside the car which is much warmer than ambient temps outside the car. But what do I know, I'm just an aerospace engineer . Thanks guys!